php中的三个关键字this,self和parent实例用法详解

<?php  
 class UserName  
 {   
     //定义属性      
     private $name;  
     //定义
构造函数
  
     function construct( $name )  
     {  
          $this->name = $name; //这里已经使用了this指针  
     }  
     //
析构函数
  
     function destruct(){}  
     //打印用户名成员函数  
     function printName()  
     {  
          print( $this->name ); //又使用了this指针  
     }  
 }  
 //实例化对象  
 $nameObject = new UserName( "heiyeluren" );  
 //执行打印  
 $nameObject->printName(); //输出: heiyeluren  
 //第二次实例化对象  
 $nameObject = new UserName( "PHP" );  
 //执行打印  
 $nameObject->printName(); //输出：PHP  
 ?>

<?php  
     class Counter  
     {  
         //定义属性，包括一个静态变量  
         private static $firstCount = ;  
         private $lastCount;  
         //构造函数  
         function construct()  
         {  
              $this->lastCount = ++selft::$firstCount; //使用self来调用静态变量,使用self调用必须使用::(域
运算符
号)  
         }  
         //打印最次数值  
         function printLastCount()  
         {  
              print( $this->lastCount );  
         }   
     }  
 //实例化对象  
 $countObject = new Counter();  
 $countObject->printLastCount(); //输出   
 ?>

<?php  
 //基类  
 class Animal  
 {  
     //基类的属性  
     public $name; //名字  
     //基类的构造函数  
     public function construct( $name )  
     {  
          $this->name = $name;  
     }  
 }  
 //派生类  
 class Person extends Animal //Person类继承了Animal类  
 {  
     public $personSex; //性别  
     public $personAge; //年龄  
     //继承类的构造函数  
     function construct( $personSex, $personAge )  
     {  
          parent::construct( "heiyeluren" ); //使用parent调用了父类的构造函数  
          $this->personSex = $personSex;  
          $this->personAge = $personAge;  
     }  
     function printPerson()  
     {  
          print( $this->name. " is " .$this->personSex. ",this year " .$this->personAge );  
      }  
 }  
 //实例化Person对象  
 $personObject = new Person( "male", "");  
 //执行打印  
 $personObject->printPerson(); //输出：heiyeluren is male,this year   
 ?>